Page 50 of 50 Reference list [1] Ceylon Electricity Board, “Long Term Transmission Development Plan 2011-2020”, July 2011, pp 5-7. [2] Siemens Energy Inc., “PSS®E 32.0 Program Operation Manual”, Siemens Power Technologies International, New York, USA, 2009. [3] Ceylon Electricity Board, “Statistical Digest 2013”. [4] Urban Development Authority “City of Colombo Development Plan 2020”. [5] ABB Ltd., “XLPE Land Cable Systems User’s Guide – Rev 5”, pp 11-12.
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Transcript
Page 50 of 50
Reference list
[1] Ceylon Electricity Board, “Long Term Transmission Development Plan 2011-2020”,
July 2011, pp 5-7.
[2] Siemens Energy Inc., “PSS®E 32.0 Program Operation Manual”, Siemens Power
Introduction .................................................................... 3Design, installation and testing ........................................ 4 XLPE cables ............................................................... 4 Cable accessories ....................................................... 4 Installation of XLPE cable systems ............................... 5 Testing of XLPE cable systems .................................... 5XLPE cable and cable system standards .......................... 6 IEC ............................................................................. 6 CENELEC ................................................................... 6 ICEA ........................................................................... 6 ISO Standards ............................................................ 6XLPE land cable system configurations ............................ 7 Trefoil and flat formation .............................................. 7 Bonding of metallic screens ......................................... 7Current rating for XLPE land cable systems ...................... 8 Current rating for single-core cables ............................ 9 Rating factors ............................................................. 11 Overload capacity ....................................................... 12 Short-circuit currents .................................................. 12 Dynamic forces during short circuit events ................... 13Cable drums - testing - cable handling ............................ 14 Selection of cable drum ............................................... 14 Testing of XLPE cables ................................................ 15 Cable handling ............................................................ 15XLPE Cable Design ......................................................... 16 Conductors ............................................................... 16 Insulation .................................................................... 17 Metallic screen ............................................................ 17 Non-metallic outer sheath ........................................... 18 Conductive outer layer ............................................... 18 Flame retardant outer layer .......................................... 18 Fire behavior ............................................................... 18Technical data for XLPE land cable systems ..................... 19Formulae ........................................................................ 23Support .......................................................................... 24Checklist for Cable Inquiry .............................................. 25
XLPE Land Cable Systems
CONTENT
To make sure you have the latest version of this brochure, have a look at www.abb.com/cables
ABB | XLPE Land Cable Systems 3
INTRODUCTION
Interfaces you can trustABB manufactures land and submarine power cables up to the highest voltages available.
Furthermore, we produce associated joints, terminations and other accessories for all types of cables. The products are designed to work together as a cable system.
Experience you can rely onWe have extensive experience of cable projects all over the world, encompassing every aspect from planning to commis-sioning, including engineering, route surveys, cable-laying, installation and final testing. Very few manufacturers can point to such a long tradition in the high voltage field as ABB. We delivered our first electrical cable in 1883 and introduced triple-extruded XLPE cables around 1970. In the early 1970s we started to supply cables for over 100 kV and our first 245 kV XLPE cable was put into service in 1978. ABB has since then supplied more than 8,800 km of XLPE cables above 100 kV. Experience you can rely on.
Research and developmentABB has always been a pioneer in the high voltage field and we have many world’s first and world records among our references. But there are no shortcuts to success. Maintaining our position calls for innovative research and development, backed up by the wealth of know-how we have accumulated over the years. One of the driving forces for our R&D is to meet the new and constantly increasing requirements from the power industry and a deregulated market. Today we aim to develop the solutions our customers will need tomorrow.
State-of-the-art manufacturing linesExperience and state-of-the-art expertise go hand in hand for us. We have been manufacturing cables for over 125 years and have since the beginning been one of the leading produc-ers. Our manufacturing plants are among the most modern in the world and our advanced quality system leaves nothing to chance. Every cubic millimeter of the cable has to be perfect. We design and produce cables in accordance with interna-tional and national standards or/and according to our custom-ers’ specifications.
This guide presents XLPE cables and systems for land applications mainly.
4 XLPE Land Cable Systems | ABB
DESIGN, INSTALLATION AND TESTING
XLPE cables
XLPE cables consist of the following components: − Conductor
Copper (Cu) or Aluminium (Al) stranded compacted conductor or Cu segmental conductor or Cu or Al conductor with key-stone shaped profiles Longitudinal water sealing of conductor
− Triple extruded and dry cured XLPE insulation system − Metallic screen
Copper wire screen Copper tape screen Radial water sealing Metallic laminate solidly bonded to outer polyethylene sheath or Lead sheath Longitudinal water sealing of metallic screen
− Non-metallic outer sheath PE PVC Halogen free flame retardant Co-extruded conductive layer over the sheath for special sheath testing
Cable accessories
ABB’s line-up of cable accessories for ABB XLPE cable systems includes:
− Straight joints and joints with integrated screen separation for cross bonding
− Transition joints for connection of XLPE to fluid- filled cables
− Outdoor terminations with porcelain or composite insulators
− Screened separable connectors for switchgears and transformers
− Cable terminations for transformers and Gas Insulated Switchgears (GIS)
− Link boxes for earthing and cross-bonding − Distributed Temperature Sensing (DTS) Systems with
integrated optical fibre in metallic tube (FIMT)
More information about our accessories is available on www.abb.com
ABB | XLPE Land Cable Systems 5
DESIGN, INSTALLATION AND TESTING
Installation of XLPE cable systems
Installation of cable systems includes trenching, cable pull-ing, clamping of cable, cable splicing as well as mounting of accessories. High quality installation work performed by ABB certified field personnel is essential for achieving the low failure rates and reliability performance that is expected from modern underground transmission and distribution circuits.
ABB has long and extensive experience from different types of cable installations including direct burial, duct, shaft, trough, tunnel and submarine installations, but also trenchless tech-nologies like directional drilling, pipe jacking and others.
Testing of XLPE cable systems
Standard routine tests, sample tests, type tests and after lay-ing tests are normally performed according to IEC-standards. Other international or national standards may be followed upon agreement between contractor and purchaser.
Routine tests of XLPE cables and accessories − PD measurement test − High-voltage test of main insulation − Electrical test of oversheath − Visual inspection
Sample testsSample tests are carried out with a frequency according to applicable IEC standards.
− Conductor examination − Electrical resistance of conductor − Check of dimensions − Capacitance test − Hot set test − Electrical tests
After laying tests − DC voltage test of oversheath − AC voltage test of main insulation
6 XLPE Land Cable Systems | ABB
XLPE CABLE AND CABLE SYSTEM STANDARDS
ABB´s XLPE cable systems are designed to meet require-ments in international and/or national standards. Some of these are listed below.
IEC
XLPE cable systems specified according to IEC (International Electrotechnical Commission) are among many other stand-ards accepted. IEC standards are considered to express an international consensus of opinion.
Some frequently used standards are:
IEC 60228Conductors of insulated cables.
IEC 60287Electric cables - Calculation of the current rating.
IEC 60332Tests on electric cables under fire conditions.
IEC 60502Power cables with extruded insulation and their accessories for rated voltage from 1 kV (Um=1,2 kV) up to 30 kV (Um=36 kV).
IEC 60840Power cables with extruded insulation and their accesso-ries for rated voltage above 30 kV (Um=36 kV) up to 150 kV (Um=170 kV). Test methods and requirements.
IEC 60853Calculation of the cyclic and emergency current rating of cables.
IEC 61443Short-circuit temperature limits of electric cables with rated voltages above 30 kV (Um=36 kV).
IEC 62067Power cables with extruded insulation and their accessories for rated voltage above 150 kV (Um=170 kV) up to 500 kV (Um=550 kV). Test methods and requirements.
CENELEC
In Europe, cable standards are issued by CENELEC. (Europe-an Committee for Electrotechnical Standardization.) They are as a rule implementations of the IEC specifications. Special features in design may occur depending on national condi-tions.
HD 620 Distribution cables with extruded insulation for rated voltages from 3.6/6 (7.2) kV up to and including 20.8/36 (42) kV.
HD 632 Power cables with extruded insulation and their accesso-ries for rated voltage above 36 kV (Um=42 kV) up to 150 kV (Um=170 kV). Part 1- General test requirements. Part 1 is based on IEC 60840, and follows that standard closely. HD 632 is completed with a number of parts and subsections for different cables intended to be used under special condi-tions which can vary nationally in Europe.
ICEA
For North America cables are often specified according to ICEA (Insulated Cable Engineers Association, Inc.).
S-97-682Standard for utility shielded power cables rated 5-46 kV.
S-108-720Standard for extruded insulated power cables rated above 46 through 345 kV.
ISO Standards
ABB has well-developed systems for quality and environ-mental management which put the needs and wishes of the customer first. Our systems comply with the requirements of ISO 9001 and ISO 14001 and are certified by Bureau Veritas Quality International.
ISO 14001 and ISO 9001 Certificate of Approval
ABB | XLPE Land Cable Systems 7
XLPE LAND CABLE SYSTEM CONFIGURATIONS
Trefoil and flat formation
The three cables in a 3-phase circuit can be placed in differ-ent formations. Typical formations include trefoil (triangular) and flat formations. The choice depends on several factors like screen bonding method, conductor area and available space for installation.
Bonding of the metallic screens
The electric power losses in a cable circuit are dependent on the currents flowing in the metallic sheaths of the cables. Therefore, by reducing or eliminating the metallic sheath currents through different methods of bonding, it is possible to incresase the load current carrying capacity (ampacity) of the cable circuit. The usual bonding methods are described below:
Both-ends bondingA system is both ends bonded if the arrangements are such that the cable sheaths provide path for circulating currents at normal conditions. This will cause losses in the screen, which reduce the cable current carrying capacity. These losses are smaller for cables in trefoil formation than in flat formation with separation.
Single-point bondingA system is single point bonded if the arrangements are such that the cable sheaths provide no path for the flow of circulat-ing currents or external fault currents. In such case, a voltage will be induced between screens of adjacent phases of the cable circuit and between screen and earth, but no current will flow. This induced voltage is proportional to the cable length and current. Single-point bonding can only be used for limited route lengths, but in general the accepted screen volt-age potential limits the length.
Cross-bondingA system is cross-bonded if the arrangements are such that the circuit provides electrically continuous sheath runs from earthed termination to earthed termination but with the sheaths so sectionalized and cross-connected in order to eliminate the sheath circulating currents. In such case, a voltage will be induced between screen and earth, but no significant current will flow. The maximum induced voltage will appear at the link boxes for cross-bonding. This method permits a cable current-carrying capacity as high as with single-point bonding but longer route lengths than the latter. It requires screen separation and additional link boxes.
Trefoil or flat formation
8 XLPE Land Cable Systems | ABB
The XLPE cable should at least have a conductor cross section area adequate to meet the system requirements for power transmission capacity. The cost of energy losses can be reduced by using larger conductor.
Load losses in XLPE cables are primarily due to the ohmic losses in the conductor and the metallic screen. XLPE cables can be loaded continuously to a conductor temperature of 90°C.
The dielectric losses in the XLPE insulation system are present also at no load current and depend primarily on the magnitude of the operating voltage.
Dielectric losses in XLPE cables are lower than for EPR and fluid-filled cables.
CURRENT RATING FOR XLPE LAND CABLE SYSTEMS
Continuous current ratings for single-core cables are given in tables 1-4. The continuous current ratings are calculated according to IEC 60287 series of standards and with the fol-lowing conditions:
− One three-phase group of single-core cables
− Ground temperature 20°C − Ambient air temperature 35°C − Laying depth L 1.0 m − Distance “s” between cable
axes laid in flat formation 70 mm + De
− Ground thermal resistivity 1.0 Km/W
Rating factors for single-core cables are given in Tables 5-13.
ABB | XLPE Land Cable Systems 9
CURRENT RATING FOR XLPE LAND CABLE SYSTEMS
Current rating for single-core cables, ampères
Table 1
Rated voltage 45-66 kV, aluminium conductor – 35 mm2 screen
Rating factors for cross section area of the metal screen of single core cables.
The rating factor is applicable to single-core cables in flat and trefoil formation with the screens bonded at both ends.
The rating factor does not apply to single-point bonding or cross-bonded systems.
Table 5 45-66 kV 35 mm2 screen
Rating factor for tables 1 and 2
Conductor mm2
Al Cu 35 50 95 150 240 300
300 1 0.99 0.98 0.97 0.96 0.95
500 300 1 0.99 0.97 0.95 0.93 0.93
800 500 1 0.99 0.96 0.93 0.90 0.90
1200 630 1 0.99 0.95 0.92 0.89 0.88
2000 800 1 0.98 0.94 0.91 0.87 0.86
1200 1 0.97 0.91 0.85 0.81 0.80
2000 1 0.96 0.88 0.82 0.77 0.76
Table 6 110-500 kV 95 mm2 screen
Rating factor for tables 3 and 4
Conductor mm2
Al Cu 50 95 150 240 300
300 1.01 1 0.99 0.98 0.97
500 300 1.02 1 0.98 0.96 0.96
800 500 1.03 1 0.97 0.94 0.94
1200 630 1.04 1 0.97 0.93 0.92
2000 800 1.04 1 0.96 0.92 0.91
1200 1.07 1 0.94 0.89 0.88
2000 1.09 1 0.93 0.87 0.86
Rating factor for ground temperature
Table 8
Rating factor for ground temperature
Conductortemperature, oC
Ground temperature, oC
10 15 20 25 30 35 40 45
90 1.07 1.04 1 0.96 0.93 0.89 0.84 0.80
65 1.11 1.05 1 0.94 0.88 0.82 0.74 0.66
Table 9
Rating factor for ground thermal resistivity
Thermal resistivity, Km/W
0.7 1.0 1.2 1.5 2.0 2.5 3.0
Rating factor 1.14 1.00 0.93 0.84 0.74 0.67 0.61
1 mm2 copper screen is equivalent to: 1.66 mm2 aluminium sheath 12.40 mm2 lead sheath
Table 10
Rating factor for phase spacingOne group in flat formation with cross-bonded or
single-bonded screens
Spacing s, mm De De+70 250 300 350 400
Cable diam, mm Rating factor
<80 0.93 1.00 1.05 1.07 1.08 1.09
81-110 0.93 1.00 1.04 1.06 1.08 1.09
111-140 0.93 1.00 1.03 1.06 1.09 1.11
Table 7
Rating factor for laying depth
Laying depth, m Rating factor
0.50 1.10
0.70 1.05
0.90 1.01
1.00 1.00
1.20 0.98
1.50 0.95
12 XLPE Land Cable Systems | ABB
CURRENT RATING FOR XLPE LAND CABLE SYSTEMS
Table 11
Rating factor for groups of cables in the ground
Distance cc
between groups,
mm
Number of groups
1 2 3 4 5 6 7 8 9
100 1 0.78 0.66 0.60 0.55 0.52 0.49 0.47 0.45
200 1 0.81 0.70 0.65 0.61 0.58 0.55 0.54 0.52
400 1 0.86 0.76 0.72 0.68 0.66 0.64 0.63 0.61
600 1 0.89 0.80 0.77 0.74 0.72 0.70 0.69 0.69
800 1 0.91 0.83 0.81 0.78 0.77 0.75 0.75 0.74
2000 1 0.96 0.93 0.92 0.91 0.91 0.90 0.90 0.90
Rating factor for cables installed in pipes in the ground
The rating factor given for single-core cables partially installed in separate pipes, applies only when a cable section between screen earthing points must be partially laid in pipes, under the following conditions:
− the cables are laid in trefoil formation over the major portion of the section
− the pipes are laid in flat formation − the piped length is less than 10% of the section
between earthing points − one cable per pipe − the pipe diameter is two times the cable diameter.
Table 12
Rating factor for cables in pipes in ground
Single-core cables
partially in-stalled in
separate pipes
Single-core cables in
separate pipes
Single-core cables in
a common pipe
Three-core cable
in a pipe
0.94 0.90 0.90 0.90
Example of the use of rating factors2 groups of 66 kV XLPE cables with aluminium conductors 1 x 500/150 mm2 in the ground in trefoil formation. Metal screens bonded at both ends, 90°C conductor temperature. Table 1 gives current rating 610 A, unadjusted value.
Table Rating factor
Current rating 610 A 1 -
Screen area 150 mm2 5 0.95
Laying depth 1.5 m 7 0.95
Ground temperature 30ºC 8 0.93
Ground thermal resistivity 1.5 Km/W 9 0.84
Distance between groups 400 mm 11 0.85 (2 groups)
Overload capacity
An XLPE cable may be overloaded up to 105°C. Singular emergency events are not expected to have any significant impact on the service life of the cable. The number of and the duration of overloads should be kept low, though. Cyclic and emergency ratings can be calculated according to IEC publication 60853.
Short-circuit currents
During short circuit events the maximum allowable tempera-ture in conductor or screen/metallic sheath is determined by the adjoining insulation and sheath materials. This is specified in IEC 61443 “Short circuit temperature limits of electric ca-bles with rated voltage above 30 kV (Um=36 kV). The dynamic forces between the conductors must be taken into account for cable installations.
Table 13
Rating factor for ambient air temperatureAir temperature, oC
Please note that use of rating factors gives good general indication during planning future circuits. Once a circuit layout is defined, an accurate calculation should be performed to confirm the assumptions.
Rating factor for cables installed in air
ABB | XLPE Land Cable Systems 13
CURRENT RATING FOR XLPE LAND CABLE SYSTEMS
Copper screens may reach a temperature of 250oC without damaging adjacent insulating material. With an initial tempera-ture of 50oC this corresponds to a current density of 165 A/mm2 during 1s (both higher and lower current densities may be allowed if other conditions apply).
Lead sheath temperatures of up to 210oC are permitted in connection with short circuit events. With an initial tempera-ture of 50oC this corresponds to a current density of 28 A/mm2 during 1 s.
Maximum short circuit currents due to thermal restrictionsThe thermal energy developed during a short-circuit is deter-mined by the short-circuit magnitude and duration. For design purposes, an equivalent short-circuit current with a duration of 1 sec is used according to formula below. This formula is valid for a short-circuit duration of 0.2 to 5.0 sec.
Ish= short-circuit current [kA] during time tsh
I1 = short-circuit current rating during 1 second. See the 1 second value in Table 14 for the conductor and in Table 15 for the metal screen.
tsh= short-circuit duration (sec)
For XLPE insulated conductors the maximum allowable short circuit temperature is 250oC.
Table 14
Max. short-circuit current on the conductor during 1 s, kA
Conductor temperature before the short-circuit
Crosssection
Aluminiumconductor
Copperconductor
mm2 65oC 90oC 65oC 90oC
35 3.6 3.3 5.5 5.0
50 5.2 4.7 7.8 7.2
70 7.2 6.6 11.0 10.0
95 9.8 9.0 14.9 13.6
120 12.4 11.3 18.8 17.2
150 15.5 14.2 23.5 21.5
185 19.2 17.5 29.0 26.5
240 24.8 22.7 37.6 34.5
300 31.1 28.3 47.0 42.9
400 41.4 37.8 62.7 57.2
500 51.8 47.2 78.4 71.5
630 65.2 59.5 98.7 90.1
800 82.8 75.6 125 114
1000 104 94.5 157 143
1200 124 113 188 172
1400 145 132 219 200
1600 166 151 251 229
2000 207 189 313 286
per mm2 0.104 0.0945 0.157 0.143
Table 15
Max. short-circuit current on the screen during 1 s, kA
Metallic screencross section, mm2
Metallic screen temperaturebefore the short-circuit
Copper screen Lead sheath 50oC 70oC
35 206 5.8 5.4
50 295 8.3 7.7
95 560 16 15
150 884 25 23
300 1768 50 46
per mm2 Cu 0.165 0.153
per mm2 Pb 0.028 0.026
Dynamic forces during short circuit events
In addition to the thermal stresses, the dynamic forces in the cables and accessories during a short circuit event must also be considered.
The dynamic effect of parallel conductors carrying current is responsible for the dynamic force.
The dynamic force between two conductors, can be calcu-lated as:
Where; Ipeak = 2.5 Ish [kA]
Ish = Short-circuit current [kA] RMS
S = Centre to centre spacing between conductors [m]
F = Maximum force [N/m]
14 XLPE Land Cable Systems | ABB
Selection of cable drum
Wooden drums/reels are standardized. For certain purposes steel drums/reels are applicable. Both wooden and steel-drums can be obtained for special purposes with other dimensions than stated below.
Table 16
Cable lenghts in meters on standard wooden drums and steel drums
Dia. Wooden drum Steel drum
mm K16 K18 K20 K22 K24 K26 K28 K30K321-
20K321-
22St 30 St 32 St 34 St 35 St 36 St 37 St 38 St 39 St 40
CABLE DRUMS - TESTING - CABLE HANDLINGSizes and weights of wooden drums and steel drums
Large and special drumsSteel drums with larger outer diameters are available, but transport restrictions have to be considered. Special low-loading trailers and permits from traffic authorities might be needed depending on local regulations and conditions.
Special wooden drums with larger barrel diameter or larger width are also available.
Table 19
Minimum bending radius for single core cables
Std cable design* Special cable design**
At laying 15 De 18 De
When installed 10 De 12 De
De is the external diameter of the cable
Cable handlingMinimum bending radius
Testing of XLPE cables
Maximum pulling forcesThe following pulling forces should not be exceeded:Aluminium conductors 40 N/mm2 (4 kg/mm2)Copper conductors 70 N/mm2 (7 kg/mm2)
Maximum side wall pressure (SWP)The following SWPs should not be exceeded:Buried installation (rollers placed close) 500 kg /m*Duct installation 750 kg/m*
* Depending on cable design and installation conditions higher values may be accepted.
Steel drums - drum type
St 30 St 32 St 34 St 35 St 36 St 37 St 38 St 39 St 40
Rated voltage and corresponding test voltages according to IEC
Type test Routine tests
Nominalvoltage
Impulsevoltage
AC voltage test
Partial discharge
test at
kV kV kVDurationminutes
kV
45 250 65 30 39
66 325 90 30 54
110 550 160 30 96
132 650 190 30 114
150 750 218 30 131
220 1050 318 30 190
275 1050 400 30 240
330 1175 420 60 285
400 1425 440 60 330
500 1550 580 60 435
Tests according to other standards can be carried out upon agreement.
16 XLPE Land Cable Systems | ABB
Conductors
XLPE CABLE DESIGN
Table 20
IEC
Cross sectionDiameterapprox.
Maximum d.c. resistanceat 20oC, ohm/km
mm2 kcmil mm aluminium copper
95 187 11.2 0.320 0.193
120 237 12.8 0.253 0.153
150 296 14.2 0.206 0.124
185 365 15.9 0.164 0.0991
240 474 18.0 0.125 0.0754
300 592 20.5 0.100 0.0601
400 789 23.1 0.0778 0.0470
500 987 26.4 0.0605 0.0366
630 1243 30.2 0.0469 0.0283
800 1579 33.9 0.0367 0.0221
1000 1973 37.9 0.0291 0.0176
1200 2368 44* 0.0247 0.0151
1600 3158 52* 0.0186 0.0113
2000 3944 56* 0.0149 0.0090
2500 4931 66* 0.0120 0.0072
Table 21
ICEA
Cross sectionDiameterapprox.
Nominal d.c. resistanceat 20oC, ohm/km **
AWG kcmil mm2 mm aluminium copper
3/0 85 10.7 0.383 0.206
4/0 107 12.1 0.269 0.164
250 127 13.2 0.228 0.139
300 152 14.5 0.190 0.116
350 177 15.6 0.162 0.0990
500 253 18.7 0.114 0.0695
750 380 23.0 0.0759 0.0462
1000 507 26.9 0.0563 0.0347
1250 633 30.2 0.0454 0.0278
1500 760 33.5 0.0380 0.0231
1750 887 36.2 0.0325 0.0198
2000 1013 38.0 0.0285 0.0173
2500 1267 45* 0.0230 0.0140
3000 1520 48* 0.0189 0.0117
3500 1773 52.5* 0.0164 0.0100
4000 2027 55* 0.0143 0.0087
1 ohm/100 ft = 3.28 ohm/km
Standards – IEC and ICEAConductors are manufactured according to the following standards:
IEC (International Electrotechnical Commission) Standard Publication 60228, Class 2: Stranded circular or shaped con-ductors of copper or aluminium.
ICEA, Standard Publication No. S-97-682, further specified in ASTM B 400-18 for aluminium, ASTM B 496-81 for copper.
* Segmented Cu conductor including tapes
* Segmented Cu conductor including tapes** The maximum value can be 2% higher
Conductor water sealingIf required, the conductor can be water sealed by:
− Swelling material between the conductor strands. This material turns into jelly when in contact with water.
− Filling compound between the conductor strands.
ABB | XLPE Land Cable Systems 17
XLPE CABLE DESIGN
Conductor screenThe conductor screen consists of an extruded layer firmly bonded to the XLPE insulation. A very smooth material is used to obtain good electrical performance.
XLPE insulationThe XLPE insulation is extruded simultaneously with the con-ductor screen and the insulation screen, e.g. triple extrusion. The interface surfaces between insulation and conductive screens are not exposed at any stage of the manufacturing. High quality material-handling systems, triple extrusion, dry
curing and super-clean XLPE materials guarantee high qual-ity products. The insulation thickness is determined by the design electrical stresses for AC or impulse. The actual thick-ness for different voltage levels and conductor sizes is given in Tables 22 to 32.
Insulation screenThis screen consists of an extruded layer firmly bonded to the XLPE insulation. The material is a high quality conductive compound. The interface between the screen and the insula-tion is smooth.
Copper wire screen, standard designA polymeric sheath covers the copper wire screen.
Metallic screen
Copper wire screen, water tight designRadial water sealing is achieved by using a metal-PE laminate. The metal is normally aluminium. Copper may also be used. The laminate is bonded to the polyethylene, which gives excellent mechanical properties. Longitudinal water sealing is achieved by using a water swelling material at the copper wires or swelling powder between the screen wires.
Lead sheathRadial water sealing achieved by a corrosion resistant lead sheath. Longitudinal water sealing is achieved by using a wa-ter swelling material applied under the lead sheath.
Copper tape screenCross section defined by the geometrical cross section of the copper tapes.
Insulation
18 XLPE Land Cable Systems | ABB
Non-metallic outer sheath
PE or PVC are normally used for the non-metallic outer sheath. IEC 60502 recommends a thickness of t = 0.035 x D + 1.0 mm, where D is the diameter under the sheath. For heavy installations a larger thickness is recommended. PE is the first choice for most applications. PVC is used when there are high requirements on fire retardation behaviour.
Conductive outer layer
A conductive outer layer facilitates testing of the non-metallic outer sheath. This testing is important to ensure the physical integrity of the cable from time to time, either in factory, after transportation, directly after laying, upon completion of the installation, or periodically thereafter.
A conductive outer layer obtained by simultaneous extrusion with the non-conductive outer sheath presents superior elec-trical and structural properties.
Flame retardant outer layer
For PE-sheathed cables a halogen free and flame retardant layer can be applied in order to limit the fire spread in build-ings and tunnel installations.
Fire behavior
This relates to cables in buildings and tunnels.
Several serious fire accidents have focused attention on the fire behaviour of cables. Experience shows that cables seldom initiate fires. However, in some cases cable installations have influenced the extent of a fire, as a propagator of flames and/or as a source of intense aggressive smoke.
Cables having a PVC sheath are considered as flame retard-ant. However, once PVC is on fire, it generates hydrochlo-ric acid fumes (HCl) acid. This gas is highly corrosive and irritating to inhale. Cables with a standard PE outer sheath do not generate any corrosive HCl but are not flame retard-ant. Special polyolefines with flame retardant properties but without chlorine or any other halogenes are optional for the outer sheath.
XLPE CABLE DESIGN
ABB | XLPE Land Cable Systems 19
TECHNICAL DATA FOR XLPE LAND CABLE SYSTEMS
Table 22
Single-core cables, nominal voltage 45 kV (Um = 52 kV)
Where ε = relative permittivity of the insulation ro = external radius of the insulation (mm) ri = radius of conductor, including screen (mm) εr XLPE = 2.5 (Value from IEC 60287)
Where U = rated voltage (kV) f = frequency (Hz) C = capacitance (µF/km) tan δ = loss angle
Where trefoil formation: K = 1 flat formation: K = 1.26 s = distance between conductor axes (mm) rc = conductor radius (mm)
Formula for capacitance Formula for dielectric losses
Formula for inductance
Formula for inductive reactance
Where f = frequency (Hz) L = inductance (mH/km)
Conductor screen:
Formula for electric stress
ri = radius of conductor screenro = radius of XLPE insulationUo = voltage across insultaion
Insulation screen:
ro XLPE
ri
Formula for maximum short circuit currents
Ish = short-circuit current during time tsh
I1 = short-circuit current rating during 1 second. See the 1 second value in tables 14 for the conductor and in Table 15 for the metallic screen.tsh = short-circuit duration (sec)
For XLPE insulated conductors the maximum allowable short circuit temperature is 250oC.
Formula for calculation of dynamic forces between two conductors
Where; Ipeak = 2.5 Ish [kA] Ish = short-circuit current [kA] RMS S = centre to centre spacing between conductors [m] F = maximum force [N/m]
24 XLPE Land Cable Systems | ABB
SUPPORT
The transmission network in most countries is very large and complex. It may incorporate many different types of transmis-sion circuits, including AC and DC over-head lines, fluid-filled cable systems and extruded cable systems, etc. Also, many modern networks contain extensive land and submarine cable systems for supply of major metropolitan areas and for inter-connection with neighbouring countries.
ABB’s experienced project managers, technical specialists and other staff will give their professional support in evaluating suitable solutions. We aim to offer the most optimal solution and we can supply the complete land or submarine cable system which can include:
− Power cables for land or submarine applications
− Cable accessories − Control- and telecommunication cables − System design for network optimization − Project management − Civil works − Installation and supervision − Testing and start-up operations − Disassembly and recovery of old cables − Fault localization and cable repair − Maintenance of fluid-filled systems − Leasing of installation equipment − Training
NOTE: All data given in this brochure are non-binding and indicative only
ABB | XLPE Land Cable Systems 25
CHECKLIST FOR CABLE INQUIRY
ABB is always prepared to work closely with our customers to develop optimized and cost effective cable system design solutions. In order for us to identify the best overall design solution for a specific application, we kindly request that the
below data checklist is submitted with each inquiry (if some of the requested data is not available at the time of the inquiry or does not appear applicable, just insert N/A in the correspond-ing data cell).
Technical information
Cable system input:
Maximum System Voltage Umax * kV
Nominal System Operating Voltage U * kV
Continuous current capacity * A/MVA
Maximum symmetrical short-circuit *current and duration
kA/s
Maximum earth-fault current and duration * kA/s
Route length * m
Conductor: copper/aluminum, cross-section Cu/Al, mm
Longitudinal water protection * Yes/No
Radial water protection * Yes/No
Any special cable design requirements Customer specification
Installed in air * Yes/No
Air temperature, maximum °C
Installed in trough Yes/No
If trough, inside dimension of trough (width • height) mm • mm
If trough, filled or unfilled
Exposed to solar radiation Yes/No
Direct buried installation * Yes/No
Soil, ground temperature at laying depth °C
Laying depth mm
Thermal resistivity backfill K•m/W
If drying out, thermal resistivity dry backfill close to cable K•m/W
Backfill material: selected sand, CBS, etc
Special requirements for trench
Cables in ducts or pipes, buried ducts * Yes/No
Material: PVC, PE, Fibre, steel, etc
Distance between ducts/pipes mm
Outside duct/pipe diameter mm
Inside duct/pipe diameter mm
Ambient temperature at burial depth °C
Thermal resistivity of ground K•m/W
Thermal resistivity of backfill K•m/W
If drying out, thermal resistivity dry backfill close to duct K•m/W
Laying depth mm
Backfill material: selected sand, CBS, etc
Termination
Type of termination and quantity. Indoor, outdoor, AIS, GIS, transformer, etc.
Type * Qty *
Special requirements - pollution level, rod gap, polymer insulator, etc.
Joints
Type of joint and quantity - premoulded, vulcanized, sectionalized, straight etc.
Type * Qty *
Special requirements
Link boxes
Type of link box
Special requirements
Other accessories
Other relevant information
Accessories
Routine, sample and after installation test. IEC, other
Type test requirements. IEC, other
Other test requirements
Tests
Cable configuration: Flat/Trefoil
Number of parallel circuits *
Distance between parallel circuits mm
Heating from existing cables Yes/No
If yes, distances to and losses of parallel cables mm, W/m
Other heat sources, distance to and losses of sources mm, W/m
Screen earthing (Both ends, Cross, Single)
Installation data
* Required informationCommercial information
Name of project *
Customer *
Location of site for delivery *
Inquiry for budget or purchase *
Tender submission date *
Do any special conditions apply
How long should the tender be valid *
Required delivery/completion time *
Terms of delivery (FCA/CPT etc.) *
Specific requirements on cable length per delivered drum
Do any specific metal prices apply
Installation: Turnkey by ABB Installation by ABB Supervision by ABB
*
* Required information
* Required information
* Required information
* Required information
26 XLPE Land Cable Systems | ABB
NOTES
ABB | XLPE Land Cable Systems 27
NOTES
Contact us
2010
-04,
2G
M 5
007
GB
rev
5ABB’s high voltage cable unit in SwedenPhone: +46 455 556 00 Fax: +46 455 556 55 E-Mail: [email protected] www.abb.com/cables